Wiklund, Christer

Wahlberg, Niklas

Department of Biology, University of Turku.

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(English)Manuscript (preprint) (Refereed)

Abstract [en]

The direction of a coevolutionary interaction can differ between local populations as in the butterflies Leptidea sinapis and L. reali. The morphologically virtually identical sister-species have partitioned their niches differently in different parts of their distribution by shifting habitat specialist and generalist roles between different sympatric areas. Hence, a species that is a generalist in some areas can be a local specialist in others, and vice versa. We have sequenced the mitochondrial COI gene from specimens collected across Europe in order to (i) describe the between-species variation over a large area, (ii) identify possible glacial refugia and re-colonisation routes to obtain a phylogeographic hypothesis for explaining the geographic mosaic of niche separation and (iii) apply a population genetic approach to determine the level of intraspecific genetic differentiation. The results show evidence for species distinctiveness throughout Europe. Only small variation was found in L. reali, whereas the haplotype network of L. sinapis showed a deep division into two haplotype families of which one was restricted to Spain and the other was widespread over the continent (including Spain). The widespread haplotype family was divided into two common variants, one eastern and one western, each being surrounded by rare haplotypes. The both deep and shallow genetic differentiation implies that L. sinapis might have been divided into different refugia during several glaciations. Both species showed significant genetic differentiation in pairwise ФST, and as habitat generalist populations could differ significantly from other habitat generalist populations but not from habitat specialist populations, we conclude that this study supports that the geographic mosaic of niche separation is caused by local processes rather than common ancestry of local habitat generalists or specialists within each species

Friberg, Magne

Stockholm University, Faculty of Science, Department of Zoology.

2009 (English)Doctoral thesis, comprehensive summary (Other academic)

Abstract [en]

Studies of ecology and evolution have become largely integrated, and increasing attention is paid to the role of ecology for speciation and post speciation divergence. In this thesis I have applied an in-depth approach studying the ecology of a butterfly species pair; the morphologically virtually identical sister-species, the Wood white (Leptidea sinapis) and Reál’s wood white (Leptidea reali). PAPER I showed a quite deep between-species division in sequence data from mitochondrial DNA. The reuniting in secondary contact zones might in contrast be quite recent, as males of L. sinapis and L. reali cannot distinguish between con- and heterospecific females (PAPER II) and since the between-species niche separation is incomplete (PAPER III, IV, V). Furthermore, the two species have partitioned their niches in different directions in different European regions as the two species shift habitat generalist and specialist roles throughout their joint distribution (PAPER III). However, the local niche partitioning has resulted in species-specific adaptations in terms of propensity to enter diapause (PAPER III, V, VI), host plant acceptance (PAPER V), and in ability to use host plant as cue for the decision to enter diapause or direct development (PAPER VI). The habitat separation is decoupled from host plant preference, at least in south central Sweden (PAPER IV), which implies that selection for niche partitioning has acted on habitat preferences directly and not via divergent selection on host plant preference. Finally, there is a high cost of appearing at a site where the other species is in the majority as much time (PAPER VII) and energy (PAPER II) are devoted to court heterospecific females or being courted by heterospecific males (PAPER VII). Hence, selection likely favours habitat specialisation in the rarest species in each region, and the direction of niche separation might simply be decided by which species that reached an area first. The species that first colonises an area would then most likely become a generalist filling up all suitable habitats, whereas the second invader might be forced to specialise, as the cost of being rare is too large everywhere but in the core population. This thesis highlights the role of ecology, and especially of local processes, for post-speciation selection and character displacement.

Identifiers

Public defence

Opponent

Thompson, John N.

Department of Ecology and Evolutionary Biology, University of California, Santa Cruz.

Supervisors

Christer, Wiklund

Stockholm University, Faculty of Science, Department of Zoology.

Note

At the time of the doctoral defense, the folowing papers were unpublished and had a status as follows:
Paper 1:Manuscript. Paper 6:Manuscript. Paper 7:ManuscriptAvailable from: 2009-11-05 Created: 2009-10-27 Last updated: 2014-10-13Bibliographically approved